Metal gasket with coating layer

Abstract

A metal gasket of the invention is used for an internal combustion engine, and is basically formed of a metal plate for constituting the gasket. The metal plate includes a hole and a bead around the hole for sealing therearound. A first coating layer is formed on at least a part of an upper surface of the metal plate except an upper portion of the bead. Thus, when the gasket is used, reduction of a surface pressure formed on the bead is prevented while fluid flowing through the hole is prevented by the bead and the first coating layer. The metal plate may be combined with one or more metal plates to constitute a metal laminate gasket.

What is claimed is: 
     
       1. A metal gasket for an internal combustion engine, comprising, a first metal plate for constituting the gasket, said first metal plate having a hole, an edge portion formed around the hole, a bead formed around the edge portion for sealing around the hole, said bead projecting outwardly from an upper surface of the first metal plate, and a base portion outside the bead relative to the hole,   a first coating layer formed on the upper surface of the first meal plate at the base portion and the edge portion except the bead so that the upper surface of the first metal plate is substantially covered by the first coating layer except the bead, and   a second coating layer formed on a substantial portion of a lower surface of the first metal plate including the edge portion, a concave portion of the bead and the base portion so that when the gasket is used, reduction of a surface pressure on the bead is substantially prevented while fluid flowing through the hole is prevented from permeating over the first metal plate by the first and second coatings and the bead.   
     
     
       2. A metal gasket according to claim 1, further comprising second and third metal plates disposed on both sides of the first metal plate to thereby constitute a metal laminate gasket. 
     
     
       3. A metal gasket for an internal combustion engine, comprising, a first metal plate for constituting the gasket, said first metal plate having a hole, an edge portion formed around the hole, a bead formed around the edge portion for sealing around the hole, said bead projecting outwardly from an upper surface of the first metal plate, and a base portion outside the bead relative to the hole,   a second metal plate having a base portion situated under the first metal plate, a curved portion situated inside the hole of the first metal plate, and a flange situated above the edge portion of the first metal plate,   a first coating layer having an annular shape formed on the upper surface of the first metal plate outside the bead relative to the hole without covering the bead so that when the gasket is used, reduction of a surface pressure on the bead is substantially prevented,   a second coating layer formed under a lower surface of the first metal plate including a concave portion of the bead and the base portion except the edge portion,   a third coating layer formed under the base portion of the second metal plate, and   a fourth coating layer formed on an outer surface of the flange.